1. Field of the Invention
This invention relates generally to marking systems for enabling sight and identification of distant geographic locations or items of interest, and more particularly to a marking system having multiple regions of active and/or passive constructions independently observable by artificial vision enhancing devices and optionally the unaided human eye.
2. Background of the Prior Art
Observation of subjects for any purpose, whether personnel, vehicles, or other objects, presents a challenge in conditions of limited visibility. When attempting to locate, target, or otherwise observe a subject in darkness, it is necessary to provide some mechanism or process by which light or infrared may be detected so that the subject may be observed. The same need exists in conditions of fog, smoke, smog, dust, or any other environmental conditions that limit visibility.
One such difficulty is presented when landing an aircraft at a remote location, which process generally requires some marking on the ground to aid the pilot in safely setting the aircraft down. In unmarked locations, pilots are often forced to use as reference points a random sampling of objects that happen to be available to them. Any reference point must be easily identifiable and seen by the naked eye or through the current generation of viewing aids, comprised of a number of magnification spotting systems, mid and far infrared imagers, and light intensifying devices. If the landing occurs at night or the field of direct vision is occluded by smoke, dust or other opaque material, landing markers can typically only be identified by heat signature through thermal imagers or light intensifying devices, if available.
Conventional markers have included active or passive devices used for indicating safe demarcation areas for either military or commercial activities. The passive markers are typically visual cue devices that are manually placed. They include flags or other artificial visual land monuments. Another type of marker is an active device that operates with an auxiliary power source that is used for activation of a visual marker. Problems associated with these earlier marker devices when considering a military application include: i) their reliance on only visual indication of a marked area; ii) their lack of durability and portability; iii) their reliance on an auxiliary power source; and, iv) their limited operational capability due to the necessary fact that they function only under conditions when visible observation is possible.
U.S. Pat. No. 5,326,265 by Prevou entitled “Battlefield Reference Marking System Signal Device” discloses a flexible tarp with grommet construction that includes an infrared reflective marking on the tarp for demarking battlefield reference points.
U.S. Pat. No. 5,567,950 by Meeker et al. entitled “Bispectral Lane Marker” discloses a rigid, dihedral shaped device that uses low infrared emissivity to mark a location for a thermal imaging device.
U.S. Pat. No. 6,567,248 by Schmidt et al. entitled “Tri-Spectrum Aircraft Landing Light” discloses a light assembly that provides powered visible light, infrared light, and FLIR emission modes.
None of the aforementioned devices provides a marking system effective in sufficiently broad portions of the electromagnetic spectrum (e.g., mid, far, and near infrared regions) and in sufficient modes of operation to provide their operator with sufficient flexibility to meet specific marking needs in varying conditions.
Another difficulty is presented when attempting to calibrate separate vision enhancing systems or devices in their operational environment in environmental conditions that limit visibility. In this case, a single marker may be placed and viewed through the separate vision enhancing systems or devices, and those systems or devices may be independently calibrated to that marker. For instance, targeting systems may comprise a laser range finder/designator in conjunction with a visible light optical camera (a “DTV” or “DVO”) and a separate Forward-Looking Infrared (“FLIR”) camera. For nighttime operation, targeting is performed with the FLIR, while the laser range finder/designator (which is separate from the FLIR) is used to guide a missile to its target. For proper nighttime operation, it is important that the laser range finder/designator and FLIR be calibrated together precisely so that when the targeting FLIR is on a target, the operator knows that the laser designator is also on the target. To ensure proper calibration, bore sighting panels have been provided comprised of a brightly colored square surrounded by and itself surrounding squares of low emissivity, high reflectivity infrared material that are distinguishable with a FLIR from the brightly colored square. In use, the aircraft crew will first focus their DTV on the center of the panel, and thereafter focus their targeting FLIR on the center of the panel. Of course, such solution has limited usefulness at night or in adverse weather conditions where the operator does not have a clear view of the bore-sighting panel. At times, such panels have been provided with a light in the center of the panel to enable nighttime focusing of both the DTV and the FLIR. However, such assembly assumes that the laser designator of the system remains calibrated with the DTV, and does not enhance the ability of the FLIR to focus on the bore-sighting panel. What is required, therefore, is a marker that would enable viewing in adverse environmental conditions to confirm calibration of all elements of such a targeting system, including the DTV, FLIR, and laser range finder/designator.
Yet another difficulty is presented when attempting to identify and monitor movement and/or position of subjects at night or in adverse environmental conditions. For example, when attempting to identify or track a ground-based vehicle from the air, particularly in an area with multiple ground-based vehicles, distinguishing the particular vehicle of interest may be difficult, particularly in adverse environmental conditions. Markers have been provided consisting of panels made from very bright colors useful for identification in well-lit, unobscured environmental conditions; low emissivity, high IR reflectivity material visible when being viewed through a FLIR; and near infrared (NIR) LED's, NIR reflective tape, and NIR chem-lights viewable through night vision goggles. However, such markers have been of limited utility due to their limitation to a single viewing platform (i.e., visible light, FLIR, or night vision goggles). Moreover, while prior known low emissivity, high IR reflectivity surfaces have provided good viewing sources through FLIR equipment when new, their prolonged use causes wear of the low emissivity material, in turn providing a very limited life span. What is required, therefore, is a marking system capable of viewing in adverse environmental conditions by multiple vision enhancing equipment platforms, and preferably which provides lasting, and even more preferably a renewable, source of low emissivity, high reflectivity material.
In summary, lacking in the prior art is a sufficiently flexible and secure marking system viewable in all environmental conditions, day or night, by combining marking surfaces independently observable in different segments of the electromagnetic spectrum, such as mid and far infrared, near-infrared, and visual markers, in a single marking system effective in different segments of the electromagnetic spectrum in powered and/or non-powered operational modes.